IWNITAUCTOR 2RAINING DIVISION GENERAL INSTRUCTION DEPARTMENT THE ARMORED SCHOOL Fort Etiox, Kentucky

ADVANCED OFFICERS CLASS #1 25 FSBRUARY 1947

M ILITARY MONORAH

TITlE: The Hollow Charge

SCOPE: History, operation, present developments gnd defense methods

as applied to the hollow charge in military use.

Prepared. by: Paul A.. Baltes., (Name)

Capt..,.Cata (Rank) 0 The HolLow. Ghargi 0

Introduction

In 1939 when the mighty German Army swept through Poland they revealed to a startled world,, new and terrifying methods of warfare.

Their Blitzkreig (lightning war) involving armor and massed assault formations soon overran most of Europe# These tactics caused all nations opposing, them or expecting to oppose them, to formulate measures of deflense against this new type of land warfare. With the fall of

France and -the German Armies' successful reduction of fortressess that once had been considered impregnable, new and more pointed.-'enphasis- was placed on the use of high principles as a means of offense as well as defense. One of these Principles wa's known as the hollow or shaped charge.

History It is a known fact, that if.' an explosive with a flat surface 'is placed against a plate.,,sane damageP to the plate- will result;, and if the plate is thin enough or the explosive in enough quant ity, Penetration will be obtained. Furthermore, for a long time it ha6 been known that if some explosive near the plate was removed, greater- penetration would be obtained, although the hole would be smaller in dli ameter.P - Alson experiments have shown that if the shaped or scoopedi the cavaties in blocks of guncbtton were reproduced in the iron plates used in test firing. Expenftenting further along these" lines, he found that'this effect could be produced with almost any type of, high explo- sive .by. simply. cutting a cavity ikn the side off the explosive which was placed toward the object to be damaged.

Demolition men,, miners,, and quarry men have long applied this same stick be-o principle by cutting out small chunks of dylamite from the fore placing it in use.

This phenomenon has been variously termed the Munroe effect*

Neumhann effe6ct, hollow charge and shaped -charge----.all of which mean the same.

Prior to World Waer II commercial explosive companies in the United

States pxperirnented at some length in attempting to turn out an ex.- plosive., that' would incorporate this effect without field expedients on the part of the user. They realized that herein lay great potential-p bore ities, both in quiarry work for use in springing holes and making the holes and also in the field of under-water demolition. Thus, when war opened up the f ield of high , much re stearch had already been done along these lines;* and. this -knowledge was to aid the U.S.

Army Ordinance and Engineers greatly when they undertook the develop- ment of the hollow charge along military lines. One of the most im- 9' -3- incorporating thias theory; and the Corps of Engineers at Fort Belvoir, Virginia, began tests to develop a packaged charge

that could be used "in bore hole-.,work and in fortress reduction.

In 19 41 Army Ordinance came out with a rif le ; and wh ile

all tests showed a successful application, it was felt that it was, not

the canplete 'answer., because of the rifle recoil.. A short time later

using the ptinciple as a means of propellant, our fir*st

came into being. While it contained several bugs, it still was con-

sidered a formidable weapon; and our infantry took it with them to

Africa in 1942.where it iniediately proved its worth as the dough-.

boys' close-up anti- weapon.

Meanwhil1e our enemies were not ignorant of the military capabil-m

iti3e s of the. shafed charge.s The Germans had used this principle as-

an aerial banb and demolition charge, but frcm all available records

it was not until our bazooka proved ita worth in Africa that they

considered this theory in anti-tank defense. It first made Its appear-m

ance inGTorman hands after the invasion of Europe, as the now well-

known . They also attempted to use this etffect in artillery.

shells but penetration failed to meet standards because of the lack

of suiLtable explosives.

Our U.S. -Armv PEngineers by this time had developed the M-1 and effect itself is easily understood. (FIG. 1) As the detonating

explosive moves foreward and reaches-the apex of the liner-, the wavesM are refracted inward at almost right angles to the -line~r; then rein-

forcing themselves, they move out along the axis. This actid'n sets

up a jet with a velocity at least as high as that of the- exp losi'veQ 'tself. This jet is usually composed of three sections. (P10.11)

First, a wave front or pressure wave usually moving at a velocity that

is greater than that of the explosives:' rate of . Thi*s

wave is f ollowed by sane. finely divided material als-o traveling at

a rate exceeding that of detonation. This in turn is followed sometimes by avp-otion of the liner (particularly when the liner is of metallic

nature) not broken into fine particles but traveling in the form of a slug at a rate less than that of detonation speed.

The above jet therefore gets its penetration qualities fran the extremely high velocity and energy plus the great pressure and heat

produced. There are also certain other factors which will aff-ect penetration, but this is best explained by a diagrann (FIG. III).

Xcplosives;-Used- The penetration depends on the velocity of the jet; and since the

Jet depends 'on the accumulation of shock waves, the higher the velocity

their f irslt 1&-l shaped charge. Latexr testsb using Pent olite Prove d very *50% T.*N.T. and 50% PEI. A1 eff'ectve with a velocity of 25,.000 to 26,000of t. per second, and this explosive was used as the explosive filler ini most of our throughout the recent war.

Ex-periments are still continuing, using various R*D.X., compositions including cyclonite and cyclotol.

New- Q-eweopments With the above data in mind, it should become apparent that this hollow charge principle will play a major role in future developmenta* along both projected and stationary explosive :lines. One drawback to this principle exists in its use as an. artillery . It has been found that rotation of the shaped charge at the l0#0O0 R.P.M.'s which is produced in artillery shells reducea penetration eff ect by as mch as 50%.* This is regretable s ince art illery shells depend upon ro- tation focr stabil ity in fl1ight.. Rrpertments are continuing to f ind means to- counteract this deffiet.0

However,, both as a stat ionary explos ive. and as an unrotated projectile, the hollow charge principle has unlimited possibilities.

As a stationary explosive in a modified' form it could well replace: the conventional anti-personnel mine because of its. longer range and pin-point accuracy. It could be used to cover de-files and dead spaces- in defensive positions and as a stationary anti-tank obstacle. This -6w, thatnewazooas d will far surpass our*an dymoes

Defense

Thus far we have spoken only of the terrific offensive power of, the hollow'cbargp. However, since the etfrcbt is known also to other nations,- it is logiceal to conclude that they too are investigating this field. Mlost defensive methods now in use in our Army are highly classified, but it would be well here to dwell on'three general methods,*

The first method is the use of mil'itary tactics to reduce effect- iveness', but since this is a problem for field canders it will not be discussed here. Method number- two, is the treatment of the armor surface to pre- vent the from tokin a workable jet. This method has been tried in several forms; the use! of plates set at an angle to prevent the fine from wctking properly; the usie of spikes to break up and dis-m perse the jet af ter it was- formed;. and the use of spaced armor.* None

~of the above mentioned methods proved:, satisf'actory although spaced armor did help in some instan-es. Rapidly rotating shells and those hollow charges that lose their penetrating power rapidly with standoff

are in this class., However, modern. unr otat ed projectiles actually in-

crease their power When striking spaced armor. They explode at stand-w off values smaller than their optimum; therefore, spacingz increasea

due to its great length, high speed, and snal area of impact cuthe 71 target.- The basic principle in stopping this jet lies. in the fact that the front end of the jet is being constantly removed as it passea. throug the target material. The rate at which this jet is-removed is proportional to the qquare root of the of the target material With this simple theory 'in mind it would thenseem that the use of light material in front of armor would give more protection. thattnextra plating. However,, materials in actual practice must be able to stand the 'impact of the missile. This would mean spacing some light, dense material with homoplate and then supporting this material on the sur-W face of the base steel armor. At this point armor thickness begins to pose a limiting consideration and must be born-e in mind in future, experiments.

With the above principle as a bas is, much research is being ex!-

tende& in the fields of plastics and other light materials, which, when incorporated with homoplate will give added protection to armored

vehicles against the s~aped charge effoct.

However, it can only be concluded that present defensive measureq' against the hollow charge are inadequate and that as exn offensive

we apon it stands paramcunt in the field of high explosives. BIBLEGRH{

O'Eert, Major T. C. 0 Rlements of

Military Engineer, The Iky 1945 A. G. F. Boar #2 Test reports

Engineer Boatd Development Reaports

Tactical and Techn ical Trends- -j / * 7-H E /9 ci. t c

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